Systems safety vital arbiter employing numerical techniques

Abstract

A numerical vital relay driver serving as an independent arbiter of vital railway (control) system operation constituting a checkword translator for receiving system checkwords from a system processor in the form of "N" bit NISAL parameters and for implementing a hardware algorithm utilizing the checkwords. It also consists of variable waveform data tables, including means for translating the data in the tables into a periodic signal, wherein it is insured that only if the checkwords are present and correct within a specific check period and the operation of the hardware algorithm is correct, will the desired periodic signal be produced.

What is claimed is: 
     
       1. A numerical vital relay driver serving as an independent arbiter of vital railway system operation comprising: a checkword translator for receiving system checkwords from a system processor in the form of "N" bit NISAL parameters, said translator including a linear feedback shift register for implementing a polynomial division algorithm from said checkwords, said shift register having an output;   said translator further including variable waveform data tables having an output, and means, responsive to the respective outputs of the linear feedback shift register and the variable waveform data tables, for combining the signals therefrom, wherein it is insured that only if the checkwords are present and correct within a specific check period and the operation of the algorithm is correct, will the desired periodic signal to be applied be produced.   
     
     
       2. A numerical vital relay driver as defined in claim 1, including a storage means coupled to the input of said checkword translator for storing checkwords; and address control logic device connected to said storage means; and wherein said storage means includes a FIFO shift register. 
     
     
       3. A device as defined in claim 2, further including a control status and timing device coupled (1) to the input of said translator, (2) to an output of said FIFO shift register, and (3) to an input of said address control logic device. 
     
     
       4. A device as defined in claim 3, in which said address control logic device is coupled to another input of said storage means. 
     
     
       5. A device as defined in claim 1, further including an Exclusive Or device having a first input coupled to the data tables and a second input coupled to said linear feedback shift register; wherein the output of the Exclusive Or device provides the desired periodic signal. 
     
     
       6. A numerical vital relay driver including two checkword translators, each as defined in claim 1, the translators having respectively different frequencies of periodic output signals. 
     
     
       7. A device as defined in claim 1, further comprising: a vital relay;   vital filter means in the form of a tuned decoder coupled to the output of said checkword translator for supplying said periodic signal to the vital relay whose operation permits vital energy to be supplied to system outputs.   
     
     
       8. A numerical vital relay driver as defined in claim 7, including a storage means coupled to the input of said checkword translator for storing checkwords; and address control logic device connected to said storage means; and wherein said storage means includes a FIFO shift register. 
     
     
       9. A device as defined in claim 8, including a control status and timing device coupled to the input of said checkword translator. 
     
     
       10. A device as defined in claim 7, further including an Exclusive Or device having a first input coupled to the checkword data tables and a second input coupled to said linear feedback shift register; wherein the output of the Exclusive Or device provides the desired periodic signal.